1. Field of the Invention
This invention relates to a sheet feeding apparatus applicable to an image processing apparatus such as a photocopier, a printer, a facsimile machine, and the like and, more particularly, to a sheet feeding apparatus for feeding sheets to an image forming section and an image processing apparatus to which the sheet feeding apparatus is mounted.
2. Description of Prior Art
As a sheet feeding apparatus applying to an image processing apparatus such as a printer or the like, an apparatus has been known in which plural sheets are stacked and contained in feeding cassettes, in which a feeding roller formed in the apparatus body presses the top surface of the stacked sheets, in which the sheet is picked up and fed sheet by sheet from the topmost sheet of the stacked sheets by the rotation of the feeding roller, and in which the sheet is conveyed to an image processing apparatus (such as recording section) by intermediate conveyance roller.
For example, with a conventional recording apparatus as for an image processing apparatus, a recording sheet that has conveyed to the recording section is conveyed by the feeding roller of the recording section and the intermediate conveyance roller as described above during the subsequent recording operation. Stable conveyance is tried by synchronized drive of the feeding roller of the recording section and the intermediate conveyance roller as described above.
However, both rollers cannot make perfectly synchronized feeding due to various factors such as pulsation movements of the drive system and differences in inertia of the drive system, and therefore, slight disorders in feeding may occur, creating fogs in recording image quality.
To cancel such feeding disorders due to asynchrony between the feeding roller and the intermediate conveyance roller, there is an apparatus that the intermediate conveyance roller is not driven during recording operation after the recording sheet is conveyed to the recording section. That is, the intermediate conveyance roller is driven through a one-way clutch, and where the feeding roller in the recording section conveys the recording sheet, the intermediate conveyance roller idles by function of the one-way clutch.
With this apparatus, however, though feeding disorders due to asynchrony between the above both rollers can be avoided, the intermediate conveyance roller idles together with the conveyed sheet, thereby rendering the idling of the intermediate conveyance roller by itself loaded to the sheets, so that sheets may be subject to back tension in the recording section. Accordingly, conveyance in the recording section by feeding roller becomes unstable, so that the recording images may be disordered, and in some cases, images may be shrunk in the feeding direction.
It is an object of the invention to provide a sheet feeding apparatus enabling sheets to be stably fed without receiving interference with the intermediate conveyance roller at the image processing section such as a recording section or the like, improving sheet conveyance performance in the image processing section, and improving the recording image quality.
To accomplish the above object, a representative structure of the invention, as a sheet feeding apparatus for conveying sheets from a feeding roller to an image processing section, includes an intermediate conveyance roller disposed between the feeding roller and the image processing section; a drive source providing a rotary drive force to the intermediate conveyance roller; an intermediate conveyance roller moving mechanism for moving the intermediate conveyance roller to be projecting in a sheet conveyance route so as to be conveyable of the sheet when the drive source is driven in one rotational direction and to be escaping from the sheet conveyance route when the drive source is driven in the other rotational direction; and an intermediate conveyance roller normally feeding mechanism for rotating the intermediate conveyance roller in only one sheet feeding direction notwithstanding of the rotational direction of the drive source.
According to this sheet feeding apparatus, since the intermediate conveyance roller normally rotating in the sheet feeding direction can project in and escape from the sheet conveyance route, the sheet can be conveyed smoothly without exerting any load due to shifts in operation of the drive system.
In another aspect of the invention, a sheet feeding apparatus includes: a feeding roller rotatively driven through a one-way clutch capable of selectively outputting rotation input for feeding a sheet in a sheet by sheet manner; an intermediate conveyance roller for conveying the sheet to an image processing section; intermediate conveyance roller supporting means for supporting the intermediate conveyance roller, the intermediate conveyance roller supporting means rotatable to a position rendering the intermediate conveyance roller project in a sheet conveyance route and to a position rendering the intermediate conveyance roller escape from the sheet conveyance route; and a clutch locking mechanism for locking the one-way clutch to stop rotation output given to the feeding roller and for unlocking the one-way clutch, wherein the one-way clutch is unlocked at a time that the intermediate conveyance roller is projecting in the sheet conveyance route by rotation of the intermediate conveyance roller supporting means.
According to this sheet feeding apparatus, since the locking mechanism locks and unlocks the one-way clutch transmitting drive to the feeding roller in association with the motion of the intermediate conveyance roller, the sheet can be conveyed smoothly in releasing loads to the intermediate conveyance roller as well as the feeding roller when the sheet enters in the image processing section.